Table 5.

Cumulative average LAN and breast cancer risk stratified by night shift work since 1989 in the Nurses’ Health Study II ($n=\mathrm{109,672}$).

Exposure	No shift work since 1989		Any shift work since 1989
	Cases (n)	Fully adjusted HR (95% CI)a	Cases (n)	Fully adjusted HR (95% CI)a
LAN quintile 1 (Median $4.3{\text{nW}/\mathrm{cm}}^2/\text{sr}$)	386	Reference	185	Reference
LAN quintile 2 (Median $12.4{\text{nW}/\mathrm{cm}}^2/\text{sr}$)	469	0.98 (0.86, 1.13)	246	1.18 (0.98, 1.43)
LAN quintile 3 (Median $22.9{\text{nW}/\mathrm{cm}}^2/\text{sr}$)	472	0.96 (0.84, 1.10)	238	1.09 (0.90, 1.32)
LAN quintile 4 (Median $37.2{\text{nW}/\mathrm{cm}}^2/\text{sr}$)	515	1.01 (0.88, 1.16)	261	1.19 (0.98, 1.44)
LAN quintile 5 (Median $64.0{\text{nW}/\mathrm{cm}}^2/\text{sr}$)	511	1.04 (0.90, 1.20)	266	1.29 (1.06, 1.56)
Continuous LAN (per IQR increaseb)		1.03 (0.97, 1.09)		1.09 (1.01, 1.18)
p for interaction	0.10

Note: BMI, body mass index; CI, confidence interval; HR, hazard ratio; IQR, interquartile range; LAN, light at night; PM_2.5, particulate matter with aerodynamic diameter $<2.5\mathrm{\mu }\mathrm{m}$.

See Figure S1 for a graphical representation of this table.

^aHazard ratios are adjusted for benign breast disease history, family history of breast cancer, age at menarche, parity and age at first birth, height, white race, BMI, BMI at age 18, oral contraceptive use, mammography screening, menopausal status, smoking status, alternative healthy eating index, physical activity, marital status, living alone, personal income, region, ${\text{PM}}_{2.5}$, census-tract median home value, income, and population density.

^bAn IQR increase in cumulative average LAN is $31.6{\text{nW}/\mathrm{cm}}^2/\text{sr}$.